PROJECT SUMMARY/ABSTRACT The majority of deaths from cardiovascular disease (CVD) in US adults ages 25-54 years are associated with suboptimal diet. While diet is an important target of CVD prevention efforts in adults, intervention on the childhood diet may be more effective. Animal data suggest that early-life diet has the unique potential to modulate biological systems and durably program a child?s biology for long-term health or disease. Yet, although NHLBI?s Strategic Vision Objective 1 prioritizes understanding how diet modulates biological systems such as the micro- biome and metabolome to sustain health, only limited animal and observational adult data exist. The objective of this application is to define the molecular effects of a dietary pattern intervention on the gut microbiome and circulating metabolome in young children. This objective will be attained through an ancillary study to a funded clinical trial that tests the effects of a 12-month Dietary Approaches to Stop Hypertension (DASH) diet interven- tion on adiposity and other CVH metrics (e.g., blood pressure, lipids) in 3- to 5-year old children (n=140). Using additional participant samples, deep phenotyping and advanced bioinformatics, the proposed work will address three specific aims. First, it will test the effect of the DASH diet intervention on the gut microbiome, including abundances of microbial taxa, communities, and metabolism-related genes and transcripts. Second, it will define the associations of diet and the gut microbiome with the circulating metabolome. Using targeted and nontargeted metabolomics approaches, blood metabolites, metabolite networks, and metabolic pathways will be evaluated. Finally, in an exploratory fashion, it will probe pathways linking the diet intervention with subsequent adiposity and CVH metrics, through the gut microbiome and serum metabolome. The expected outcome is a preliminary model of how the DASH diet alters the gut microbiome and circulating metabolome in young children, and how these alterations relate to short-term CVH outcomes. These pilot data can be validated in larger samples, and thereby contribute to eventual development of novel, targeted early-life dietary strategies to preserve ideal CVH. The proposed research will also be leveraged as a training platform for Amanda Marma Perak, MD, who aims to have an independent translational research program focused on understanding early-life determinants of CVH and developing strategies to preserve life-long CVH. A team of prominent scientists will provide mentorship in a rich research developmental environment at Northwestern University and Lurie Children?s Hospital. Customized didactic, experiential, and professional development activities will complement mentored research experience to ensure that Dr. Perak attains her short-term training goals to gain expertise in, first, systems biology molecular methods and translation of mechanistic insights for clinical relevance, and second, clinical trials conduct. These plans and resources will ensure that in 5 years, Dr. Perak is a molecular epidemiologist and pediatric cardiologist who can lead multidisciplinary teams in translational research, taking new ideas through epidemiologic evalua- tion, mechanistic study, and clinical application, with a sustained impact on the field of pediatric CVH promotion.